Showing papers by "He Zhu published in 2012"

A UWB bandpass filter with wide stopband performance using cross-shaped coupled lines

Abstract: A novel coupling structure is presented for the design of an ultra-wideband (UWB) bandpass filter (BPF) with wide stopband performance. The proposed coupled structure is constructed by modifying the conventional one quarter-wavelength parallel coupled lines into cross-shaped coupled lines (CCLs), which results in size miniaturization as well as wide upper-stopband performance. The CCLs can be properly designed so that the unwanted passband is rejected and the transmission zeros can be assigned toward the harmonic resonances of the triple-mode resonator. By cooperating the proposed CCLs and the triple-mode resonator, a UWB BPF with sharp roll-off and improved out-of-band performance is then constructed. Both simulated and measured results are in good agreement to verify the predicted results.

Compact UWB bandpass filter using folded-T-shaped resonator with a notch-band

Abstract: This paper presents a compact ultra-wideband bandpass filter based on a folded-T-shaped resonator with a notch-band. Characterized by theoretical analysis, the T-shaped resonator makes it easier to control resonant modes, and two transmission zeros appear in the lower and upper stopbands to improve skirt selectivity. A narrow slot is embedded within the resonator, in order to produce a bandstop characteristic. In this way, a notched band is introduced around 5.75 GHz, and the bandwidth and coupling strength of the notch-band could be tuned easily. Finally, a filter is fabricated and measured, and the measured results are in good agreement with simulation, demonstrating good insertion/return losses as well as a notch-band application.

Ultra-wideband (UWB) bandpass filter with sharp selectivity and wide upper stopband

Abstract: A compact quadruple-mode ultra-wideband (UWB) bandpass filter with sharp selectivity and extremely wide upper stopband is proposed in this paper, using a multi-stage stepped-impedance resonator, two open-circuited ends and a pair of high-low impedance stubs. The characteristics of the proposed multimode resonator are analyzed by simulation, demonstrating that the first four resonant modes can be appropriately located in the desired passband and other resonant modes in the upper stopband can be suppressed. To improve the skirt selectivity and out-of-band performance, two identical high-low impedance stubs are introduced into the design, without changing any resonant characteristic of the filter. Finally, the improved filter is fabricated and measured, and simulated and measured results are in good agreement to show that the proposed filter has a sharp selectivity with a −21.5 dB rejection stopband extended to over 30 GHz.

A UWB bandpass filter using slotline ring resonator with a notched band

Abstract: A quadruple-mode UWB bandpass filter is presented. The proposed filter is comprised of a slotline ring resonator, which forms an ultra-wide passband with four resonant modes. Two pairs of defected ground patches are added to improve the desired passband. To achieve a wide upper stopband, a pair of defected ground dumbbell units is introduced. Moreover, a notch band is added around 5.5GHz using a U-shaped slotline to avoid wireless local-area network (WLAN) signals. Finally, a filter is fabricated and tested. Simulated and measured results are in good agreement to exhibit that the proposed UWB BPF has a passband from 3.1GHz to 10.9GHz with a notched band in 5.5GHz, and a wide upper stopband with attenuation level of −12.8 dB up to over 30GHz.